Thermostat



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IIIIIIIIIIIIIIIIIIIIIIII!!! IIII IIIIII Dec. 16, 1941. w. VAN'GUILDER THERMOSTAT Filed July 13, 1939 Patented Dec. 16, 1941 UNITED STATESPATENT OFFICE (Cl. 20G- 141) 8 Claims.

The invention relates to thermostats and more particularly to improvements in immersion thermostats of the general type used for regulating the temperature of baths or bodies of liquid and the like.

One general object of the invention is to provide a thermostat embodying a U-tube containing a body of thermally expansive and electrically conductive liquid such as mercury adapted to complete an electric circuit upon a predetermined thermal expansion, having an improved arrangement for adjusting the temperature setting of the device.

Another object is to provide an expansible liquid U-tube immersion thermostat embodying a novel arrangement of parts such as to facilitate disassembly and reassembly of the structure for purposes of cleaning or replacement of parts.

A more specific object is to provide a thermostat of the character indicated comprising a contact inserted in a separable capillary tube in which the liquid rises upon thermal expansion, characterized by the provision of a novel screw cap arrangementl for removably securing in place not only the capillary tube but also the contact.

Still another object of the invention is to provide an expansible liquid thermostat incorporating various structural improvements by virtue oi which low cost and simplicity of construction are combined with ease of adjustment and assembly, as well as accuracy of operation.

Further objects and advantages of the invention will become apparent as the following description proceeds, taken in connection with the accompanying drawing, in which;

Figure 1 is a general perspective view of a thermostat embodying the invention.

Fig. 2 is an enlarged side elevation of the thermostat of Fig. 1, in place in a bath whose temperature it is to regulate, with the upper portion of the device shown in vertical section.

Fig. 3 is a transverse sectional View along the line 3--3 in Fig. 2.

Figs. 4 and 5 are exploded perspective views of the various parts included in the assemblies located respectively on the left and right hand legs of the thermostat of Fig. 1.

For purposes of exemplication, the invention has been shown herein (Fig. 1) as embodied in an immersion thermostat of a form suitable for controlling the temperature of, for example, the oil sample in a Viscosimeter or liquid baths used in various chemical processes.

Thermostats embodying the invention may, however, take various forms depending in part upon'the particular uses for which they are intended. Accordingly, even though a particular embodiment of the invention has been shown and described in some detail there is no intention to thereby limit the invention to such embodiment, but, on the other hand, the appended claims are intended to cover all modifications and alternative constructions falling within the spirit and scope of the invention.

In the illustrative construction (Fig. 1), the thermostat shown embodies a U-shaped tubular structure, designated generally by the numeral Il), and adapted to be inserted in a bath of liquid I I (Fig. 2) whose temperature is to be regulated. The tubular structure I 0 contains a thermally expansible and electrically conductive body of liquid I2 such as mercury. In brief, expansion of the liquid I2 upon being heated causes it to rise in the tubular structure I0 and complete an electric circuit, and, similarly, contraction of the mercury upon the lowering of its temperature causes it to recede and break the circuit.

The tubular structure I0 comprises a glass U- tube I3 (Fig. 2) having upwardly facing open ends on its two legs. To give maximum sensitivity of operation a glass capillary tube I4 is arranged to form an extension of the right hand leg of the U-tube I3. This capillary tube I4 is fashioned with an axial bore I5 of very small diameter communicating with the interior of the U-tube and in which the mercury I2 rises upon thermal expansion. Since the thread of mercury received in the bore I 5 is of very small total volume only a small expansion or contraction of the main body of mercury is required to cause the mercury in the bore I5 to rise or recede from a level at which it establishes an electric circuit with an electric contact pin I6 inserted into the top of the bore I5.

To minimize the cost of the parts, the capillary tube I4 and the U-tube I3 are made as separate parts thereof. In such case, the joint between them must vbe hermetically sealed. An enlarged and tapered end I4a on the capillary tube I4 is received in a complementally flared end I3a on the U-tube I3. The abutting surfaces on the tube ends I3a and I4a are ground so as to have a snug and accurate rit.

The couplings for holding in place the part assemblies secured to the respective legs oi the U-tube I3 include sleeves I'I and I8 (Figs. 1 and 2) permanently cemented to the respective tube legs and made of electrical insulating material such as reenforced Bakelite. On the right hand leg of the U-tube I3 is mounted the capillary tube I4 heretofore described and its cooperating contact I6. On the other or left hand leg of the U-tube is mounted a device for adjusting or regulating the temperature at which the thermostat responds. l A

The contact assembly on the capillary tube I4 (Figs. 2`and 5) includes the contact pin I6 having an enlarged head Ita resting on the top of the tube. This contact pin may be made of some metal having a high electrical conductivitysuch as platinum. Resting on the top of the pin head IIa is a U-shapedlresilient' 'sheet metal'- stamping forming connecting' fingers I9 which' are resiliently urged outward into engagement with a metal ring 20 threaded inthe coupling' sleeve I8. A disk I9a welded to the base of the connecting finger strip rests in face-to-'fac' engagementv with the contact head |65. In this way the'- ngers I9 complete a circuit-from the pin I6 to the ring 2|) irrespectiveof the angular position of the pin and` iinger assembly on the capillary tube |4.

To hold both the capillary tube I4 and contact pin assembly in place, a single screw cap 27| is utilized.- This cap may be made of molded electrical insulating material such as reenforced Bakelite and is threaded on'the upper end of the ring 20. Yieldable disks 22 of cork or the like are inserted between they top wall of theV cap 2| andthe disk- I 9l so as to form a yieldable connecticn betweenV the screw cap and the parts against which it is-pressedf. The screw cap 2| is windowed as indicatedV at 23 (Fig. 1) in order that the' operator may observe the condition of the contact pin If and the' level' of thev thread of mercury in the capillary tube bore I5.

In order to adjust the temperature setting of the thermostat, ai plug 24. (Figs. 2 and 4) is ar` ranged toproject intol the left hand leg of the U-tube I3; By' moving this plug down into the U-tube a corresponding' amount of mercury is displaced and the level of the thread of mercury in the capillary tube bore I correspondingly adjusted. For this purpose, the plug 24 is mounted i'n an axial bore 2li-'fixed' in the coupling sleeve Il and is threaded in a cap 23 which is in tur-n threaded on theV exterior of the sleeve I'I. The head 2l' of the plug 24 matches in form the head of the screw cap 2| (see Fig. 1) so as to give the device asymmetrical andV pleasing appearance. The cap 26 and plug head 2lv are preferably made' of molded insulating material althoughY theY plug itself is made of electrically conductive metal, such', for example, as stainless steel, since the electricV control circuit in the thermostat is completed throughY this plug.

Terminals connected respectively toy the plug 24 and ring 20 are mounted on a supporting plate 28A (Figs. 2 and 4) made of suitable electrical insulating material. This plate is apertured to receive the ends of the U-shaped structure' I0 and is clamped against abutments on the coupling sleeves I'I, IB by the screw caps 2| and 26. In particular, the plate 28 rests on a shoulder IIa fashioned on the coupling sleeve I'I, being pressed aga-inst it by the screw cap 26 and an interposed nut 29. Similarly, the plate 28 also rests on the end of the other coupling sleeve I8 and is pressed againwstit by the screw cap 2| and an interposed n ut M29?. The edges of the plate 28 project laterally from the U-shaped structure Ill so that when the device is inserted into an aperture 30 (Fig. 2) in the top of a tank 3| the plate 28 holds it in place with the lower portion of the U-shaped structure I0 immersed in the bath II within the tank.

On the right hand leg of the thermostat the ring 2d, which is connected with the contact pin I 6 as heretofore described, is connect-ed to aterminal 32 (Fig. 3) by conductor 33. Similarly, the plug 24 at the other end of the mercury column is connected to a second terminal 34 on the cover plate 28 by a resilient wire 35. This wire 35 is bent into diamond shape (Figs. 3 and 4)' and embraces the plug 24. The resilient wire 33 is dirnensionedso that it closely and frictionally engages the plug 24 to form a good electrical connection with it and also to hold the plug fricticnally against inadvertent displacement.

Tocondition the thermostat for operation the U-tube I3 andY capillary tube I 4 are thoroughly cleanedrand then filled with mercury to sub-v stantially the normal level (Fig. 2). The various parts on the two legs of the U-shaped structure are then assembled as heretofore described and the screw caps 2| and 26 threaded into place so as to hold the parts together. The plug 24 is then adjusted in position by turning the head 21 until the thread of mercury in the capillary tube bore I5 is located at Iexactly the desired point of adjustment or normal level, as observed through the window 23.

In the operation of the thermostat described it may be located on a tank 3| as sh'own in Fig. 2 with the U-tube immersed in a bath of liquid II. The thermostat is adjusted as previously described` for some selected temperature at which the bath is to be maintained. In the event that the temperature of the bath rises above this selected temperature the mercury IZ will expand, thus causing the thread of mercury to rise in the capillary tube bore I5 until it touches the contact I 6. Thereupon a circuit i-s completed between the terminals 32 and 24 through the plug 24, mercury I2, contact pin I3, ngers I9 and ring 20. A temperature regulating or signal device connected across the terminals 32, 34 is thus actuated. Similarly, when the temperature again drops below the predetermined maximum the mercury recedes from the contact pin I 6 so as to interrupt th'e circuit previously established.

From the foregoing, it will be seen that a thermostat has been provided which, although very accurate and precise in operation, is simple to construct and easy to adjust. Furthermore, all of the parts can be quickly and easily disassembled in order to clean or repair the thermostatas may be required.

I claim as my invention:

1. A thermostat comprising, in combination, a generally U-shaped tubular structure adapted to contain akbody of thermally expansive and electrically conductive liquid, the legs of said U- shaped structure presenting shouldered upper ends, and a iiat supporting plate apertured to receive t-h'e upper ends of said legs and resting on the shoulders of said legs, and mean-s including a pair of cup shaped closure caps telescoped over and threaded on the upper ends of respective ones of said legs for clamping said supporting plate against said shoulders.

2. A thermostat comprising, in combination, a glass U-tube adapted to contain a body of thermally expansive and electrically conductive liquid, coupling sleeves xed on the upper ends of said U-tube and each presenting an upwardly facing abutment, and a supporting plate made of electrical insulating material having apertures registering with the upper ends of said U-tube and resting on the abutments on said sleeves, an electrical terminal for the device carried by said plate, and means including a pair oi cup shaped closure caps telescoped over and removably connected to said sleeves for clamping said supporting plate against said abutments.

3. In a thermostat the combination of a U- tube presenting an upwardly facing opening in at least one end thereof and adapted to contain a body of thermally expansive and electrically conductive liquid, a capillary tube removably inserted in the open end of said U-tube and having an axial bore communicating with the interior of the U-tube, an electrical contact pin projecting into the upper end of said capillary tube bore and having a head thereon resting on the upper end of said capillary tube, means including a cap of inverted cup shape telescoped over the top of said capillary tube and the head of said contact for holding the same in place, and a yieldable member interposed between the end wall of said cap and the head of said contact pin.

4. In a thermostat the combination of a generally U-shaped tubular structure adapted to contain a body of thermally expansive and electrically conductive liquid, said structure having a capillary bore in the upper end of one leg, a head-- ed contact pin projecting into the capillary tube bore, a metal ring encircling said one leg of the tubular structure, and a resilient metal spring nger tted over the head of said contact pin and yieldably urged against said ring for establishing an electrical circuit therebetween.

5. In a thermostat the combination of a generally U-shaped tubular structure adapted to contain a body of thermally expansive and electrically conductive liquid, said structure having a capillary bore in th'e upper end of one leg, a headed contact pin projecting into the capillary tube bore, a metal ring encircling said one leg of the tubular structure, and a strip of resilient metal of inverted U-shape resting on the head of said contact pin with its legs extending down along the sides of the capillary tube and resiliently urged into engagement with said ring to complete a circuit from the Contact pin to it.

6. In a thermostat the combination of a tubular structure adapted to contain a thermally expansive and electrically conductive body of liquid, an electrical contact arranged to be contacted by the liquid upon thermal expansion of the latter, an electrically conductive plunger arranged to project into the liquid to establish' a circuit to it, means supporting said plunger for axial adjustment to vary the displacement of liquid by it and thereby vary the normal level of the liquid with respect to said contact, and a resilient connecter member frictionally engaging said plunger for not only completing a circuit to it but for al-so preventing inadvertent displacement of it.

7. In a thermostat the combination of a generally U-shaped tubular structure adapted to contain a body of thermally expansive and electrically conductive liquid, said structure having a capillary bore in the upper end of one leg, a contact projecting into the capillary tube bore, a metal ring encircling said one leg of the tubular structure, and a metallic conductor extending from the upper end of said pin to said ring and removably contacting the latter for establishing an electrical circuit therebetween.

8. In a thermostat the combination of a generally U-shaped structure adapted to contain a body of thermally expansive and electrically conductive liquid, said structure having a capillary bore in the upper end of one leg, a contact projecting into the capillary tube bore, a metal ring encircling said one leg of the tubular structure and secured thereto, a metallic conductor extending from the upper end of said pin to said ring and removably contacting the latter for establishing an electrical circuit therebetween, and a housing of generally inverted cup shape telescoped down over the end of said one leg and enclosing said conductor and threaded on the exterior of said ring.

WALTER VAN GUILDER. 

